The present invention relates to a field emission device, and more particularly to a multiple micro-tips field emission device in which the uniformity of emitted current is improved so as to be used for a flat panel display.
Recently, flat image display devices have been actively developed as a replacement for the CRT (cathode ray tube) of conventional T.V. sets, in particular their use in wall-mounted (tapestry) television and high definition television (HDTV). Flat image display devices include liquid crystal display devices, plasma display panels and field emission devices. Among these, the field emission device is being concentrated on due to its image brightness and low power-consumption.
Referring to FIG. 1, the structure of a conventional field emission device is described.
The field emission device includes a glass substrate 1, a cathode 2 formed on glass substrate 1 in stripes, a micro-tip 4 for field-emission formed on cathode 2 in an array structure, an insulation layer 3 formed on cathode 2 to surround micro-tip 4, and a gate electrode 5 formed on insulation layer 3 in stripes perpendicular to cathode 2 and having a gate aperture 6 over micro-tip 4 for field emission.
To fabricate field emission device of the above structure, it is necessary to form a nanometer-sized micro-tip array. Therefore, fine processing of a submicron unit is required in the gate aperture etching process so that the gate having a precise aperture size, considering the micro-tip size (radius) can be formed, because, without such a fine processing, the gate aperture is too large, whereby a high driving bias voltage is required and the tip radius itself can affect uniformity of the flat panel display device. That is, the micro-tip radius must be under 200 .ANG., and the gap between the gate and the micro-tip must be within submicrons.
In the actual manufacturing process, nonuniformity of film thickness, nonuniformity in the micro-tip forming process and difficulty in a layer parting process remain problematic. This problem causes nonuniformity of luminance when the field emission display device is used as the flat panel display device, and nonuniformity of current emission amount when used as a very high frequency device. Particularly, since the array of a plurality of micro-tips must be fabricated uniformly in a device requiring large current emission, such as is used in a very high frequency amplifier or other electron beam-applied apparatus, a high yield cannot be obtained in the fabrication process because of the nonuniformity problem.